I'd suggest using a sheet of 80 grit sandpaper like body workers use for roughing out Bondo, folded into a square that's about 1/4 the size of the original sheet. Give the drum a vigorous scrubdown, followed by a cleanup with spray brake cleaner and a rag. Another sneaky trick to make the new brake linings wear in to the exact shape of the drum is to glue a piece of the same grit sandpaper to the inside of the drum and scuff the newly relined brake shoes against if to match the brake to the radius of the drum. Otherwise, you'll need to adjust the brakes repeatedly as the lining "wears in" to full contact with the drum. If you use a water-soluble glue like original Elmer's white glue, a quick splash of boiling water will remove the sandpaper easily.
Jerry
